Hey, you'all....
I'm new to the site, but wanted to throw in my two cents, regarding the Porsche 930. I'm running one (930 transaxle, with LSD) inverted, behind a small block Chev (yes, I know....Chev, boo...hiss). The mill has twin turbos, intercoolers, and fuel injection, and was "soft tuned" on an honest dyno at 857 HP. The torque levels are consistant with the HP readings, and come in at relatively low (2,500) RPM. I'm running the engine/transaxle in a McLaren Mk 8 clone, at 2130 lbs wet, without driver. Tires are a sticky Potenza 335-35-17 compound. I recently added active traction control (using the ABS wheel sensors on my Corvette uprights, front and rear), to modulate the ignition timing under wheel slip. The car is a street/track car, and I drive it aggressively (the logging data on my Electromotive TEC reads 0-60 MPH in about 2.9 to 3.0 seconds).
I've flogged the transaxle over the last year, and on occasions turned up the boost even a little higher than its dyno'd runs. I've never had any problems. In the past I used to break traction, which probably limited torque loading on the transaxle shafts; now with the traction control, wheel spin in minimized but still no groans from the transaxle. I have yet to add a spray bar, but probably will pull the transaxle this Spring and get it to Powerhaus in Boulder for the mod.
My comments probably don't resolve the debate, but I thought you'd like to know the Porsche 930 (at least, mine...) has held up admirably, and I suspect it will for years to come (fingers crossed).
Pics of my car attached, for those who enjoy some "outside the GT-40" box alternatives.